1. Field of the Invention
This invention is generally relative to methods and apparatuses for image processing. More specifically, this invention relates to methods and apparatuses for adjusting an image on the basis of the characteristics of a display system.
2. Description of the Prior Art
A plasma display panel (PDP) consists of millions of lighting cells regularly arranged as a matrix. Typically, the lighting cells disposed on the same horizontal line are serially connected to and jointly share a horizontal electrode set consists of a scan electrode and a sustain electrode. Each of the lighting cells is selectively corresponding to one color among red, green, and blue. With the power provided by the horizontal electrode set, gas in the lighting cells discharges electricity and accordingly generates ultraviolet. The fluorescent powder in the lighting cells is then excited by the ultraviolet to selectively generate visible red light, green light, or blue light. Furthermore, by controlling an address electrode for each of the lighting cells, the brightness of one lighting cell can be independently adjusted. That is to say, by controlling the horizontal electrode set and the address electrode, the brightness of one lighting cell can be adjusted.
As described above, all the power of the lighting cells disposed on the same horizontal line is provided by one horizontal electrode set. The power loading for the horizontal electrode set varies with the number of lighting cells being turned on. Through measurements, it can be found that when all the lighting cells on the same horizontal line are turned on, the loading for the corresponding horizontal electrode set is highest. If the power provided from one horizontal electrode set to the lighting cells is fixed, the power provided to one lighting cell is less when the number of lighting cells being turned on is larger. Hence, when more lighting cells on the same horizontal line are turned on, the brightness of the lighting cells is lower. If the loadings of two adjacent horizontal electrode sets are different, the brightness of the two corresponding horizontal lines is also different even all the gray levels of the pixels on the two horizontal lines are the same. Besides, variances in brightness due to loading variations for red lighting cell, green lighting cell, and blue lighting cell are different. Thus, the colors of the two adjacent horizontal lines are different, too. When the loadings of two adjacent horizontal electrode sets are more different, the brightness and colors of the two corresponding horizontal lines differ more from each other. This phenomenon is called loading effect of PDPs. If the loading effect is serious, people can see an obvious horizontal boundary on a PDP screen, hence the quality of an image displayed on the PDP screen is lowered.
Various techniques have been developed for lessening the loading effect of PDPs. For example, changing the structure of a PDP to reducing current and using electrodes with lower resistances to decreasing voltage drops both can lessen the loading effect of the PDPs. Another technique also useful for lessening the loading effect is increasing the driving ability of horizontal electrode sets or changing relative driving waveforms. However, these prior arts are all difficult from the viewpoints of implementation and cost.